Problem of global variables

Similar Questions

• Global Variables are preferable to the Globals functional - so there! :-)

  I feel a little controversial today so forgive the brutal title of this post

  I've never used global variables because I was under the misconception that they are somehow 'bad '. That's all I've heard since I started learning the LabVIEW. Review the code in the nets upconvert and downconvert. The ugliest code uses globals and some of the most beautiful code does not work. This means that bad programmers use global variables and globals are so bad programming practice. This is not true. Globals are just easy to use for newbies to use them. ' Not initialized what? I can't find those on the pallette? »

  I think I always wondered unconsciously that globals are bad. They are not bad, it is their use that may be bad. This is true for anything in life.

  The first and the most obvious problem with global variables is racing conditions. But this is not strictly the overall causing the race condition. This is the data stream is not defined.

  

  But the same is true if functional a global being misused. In the example below there is nothing to enforce data streams.

  

  You must run the data flow with a thread of error for example.

  

  Globals do not have a thread of error but not fear - the man of the sequence is here!

  

  You only need the sequence if the global is directly on your drawing. These two structures of single image sequence could be replaced by a NumericWrite.vi and a NumericRead.vi containing nothing but overall, a command or the indicator respectively and the terminals of the error. Put it online and it is good as gold. Or you might have a Subvi containing nothing but a frame two cases selected by an enumeration containing the elements 'Get' and 'Set '. Now, it looks like a duck and quacks like a duck. Don't you worry by the overhead of the structure of the case either. If the enum is a constant, it will be unfolded.

  Another problem with globals, it's that they are, well, global. Is not different from a functional overall, so it isn't really a problem anyway. Globals and globals functional it is easily taken by placing them in a library and define the scope of the access. Not to mention that libraries give you namespaces and "namespaces are one honking great idea - do several of these!" *

  The real reason to use a global rather than a functional overall is that they are about twice as fast.

  Until this morning I would have recommended to use a more functional global overall. But I changed my mind. Someone can it change back?

  * The Zen of Python

  
  

• global variables for the XML plugin problem

  Hello world

  recently I started working on a dialog box SOUTH, where the user can load the *.xml files in DIAdem.So much my code for the button looks like this:

  ....

  Call the FileNameGet ('ALL', 'FileRead","*.xml")
  Call DataFileLoad (FileDlgName, "XML_Plugin", "Load")

  ....

  And I must say that it works very well! I am able to load all listed in the devices file. BUT when I tried a number of loading devices, I used a global variable, that I defined in the vbscript file that I load the SOUTH since, I've noticed that global variables, I've defined with GlobalDim are not defined in the vbs.:mansurprised of XML_Pluging:

  Then I started to experiment and so far without success, no matter where I define global variables, in my plugin *.xml all not defined! The native commands even and DIAdem functrions does not work. If I run the script in tiara, it shows no errors, but when I use the plugin to open a file, then it gives an error. For example, MsgBox is not allowed.

  I used the plugin example for *.xml, which was published on the Web site of NOR, and I made a few changes. But overall I have it has not corrupted and I kept the same structure:

  Void ReadStore (File)

  Dim XmlFile: xmlFile = File.Info.FullPath
  '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
  'open the file '.
  OpenXMLFile xmlFile

  End Sub

  Void OpenXMLFile (xmlFile)
  '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
  ' Open MS - Xml Parser
  'Create the ActiveX object for the Microsoft XML parser.
  Dim XDoc: set xDoc = CreateObject ("MSXML2. DOMDocument.3.0")

  "Try to load the XML document
  If xDoc.Load (xmlFile) = False Then
  "Failed to load the document XML.
  RaiseError ' unable to load XML document!
  End If

  protected originalLocale: originalLocale = Getlocalte
  "SetLocale" en - us ".

  "The XML document loaded successfully!
  '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

  '----------------------------------------------
  "Read the header information.
  '----------------------------------------------

  Here, I have read some values of the header and then I loop on all devices present in the file!

  So basically I have two subroutines and that's all.

  SetLocale originalLocale

  End Sub

  So what I am doing wrong? Why global variables and other functions do not work. Is it because there is xml code in the script this way or it's a version problem?

  I use DIAdem 10.2. If I use global variables in other vbscripts, I use to draw curves for example I have no problem. Now I'm no *.xml code and no subroutines.

  I'd appreciate any solution that will make my *.xml plugin to work.

  Hi fscommand.

  It is expected all behavior.  Use XML, as all VBScript DataPlugins, runs in a separate VBScript host of the DIAdem VBScript host.  DIAdem VBScript host adds all global variables green and Red controls global to host Microsoft VBScript standard.  Use VBScript host has its own special abilities (file object, root object), but there is NO access to Globals green or red blanket orders in the reception of DIAdem VBScript.  Your SUDialog runs in a third host VBScript, which is separated from the other two and the other two are not capabilities (command SUDialog callback functions), but the SUDialog VBScript host and VBScript tiara share all global variables green and Red orders overall.

  Normally all blue VBScript commands are allowed in all 3 VBScripts hosts, but in the case of the DataPlugins MsgBox and InputBox functions were especially restrained because the dialogues could cause a lot of trouble with the DataFinder.  In fact, they have been allowed to 9.1 tiara which was the latest version of tiara for the DataFinder appear.

  So, why do you want to pass information between the XML use and tiara?  If you want to use to share information with DIAdem, then you should just expose every piece of information as a new property in the data portal, which can read and use the code VBScript DIAdem.  The path of the XML file is already available inside the use of XML.  What other information in the call VBScript DIAdem do you need to share with the use?

  Brad Turpin

  Tiara Product Support Engineer
  National Instruments

• Global variable problem using as reference file

  Hi all

  This code is trivial, but illustrates the problem that I have.  I want to open a file with vi a, dynamically open vi B, pass the reference file in vi B, vi B to close, and then close the fiel with A vi.  VI B is designed for SAMPLES continuously and add it to the file.  Unfortunately I can't implement this solution because it seems that global variables do not work for the file references (!).  Thank you!

  You have a race condition in this image.  The global variable refnum to could be read the file write before the opened file has been fortunate to write a valid file for the other reference copy refnum of global variable.  You should have a thread open to write it directly.  If you want to store it in the global variable as well, then branching off there this direct wiring.

• Global Variable length problem

  Hi all
  
  I'm moving a group of a pll key values.
  I'm holding all the key values in a text field that can contain up to 10000 bytes and I'm assigning the text field values to a global variable.
  This value of the global variable is read by pll and fetch the records using these key values.
  
  But I'm getting ORA-06502 error. This is a question about the length of the variable.
  Form builders help I got to know that this global variable can hold only up to 5000 bytes.
  
  Suppose that
  New_id is a text field that has more than 7000 bytes values separated by comma
  
  New_id is that a text field of type char length is 10000,
  
  +: global .new_cust_id: = Block.new_id +;
  
  On this line, I get ORA-06502 error, because this value is used by other packages.
  
  Can someone help how do I fix this
  
  Use forms [32 bit] Version 11.1.1.4.0 (Production) and Oracle database 11 g R2
  
  Thank you
  malandain

  Citing the Globals online documentation:

  A global variable is a variable of Oracle Forms whose value is available for the triggers and the subprogrammes in any module that is active in the current session. In previous versions of Oracle Forms, a global variable stores a string of length, for all uses up to 255 bytes. In Oracle 10g form, global variables are now limited to 4000 bytes when they are set or referenced using PL/SQL bind variable notation. for other uses, no limit is imposed.

  This means: If you access the global variable like this:

  :global.variable := value;
  

  You can store up to 4000 bytes in length. If you use the copy and name_in built ins you should be able to store up to 32767 bytes in a global variable.

  see you soon

• Loading a file into a global variable problem - really a global var text?

  Of all the documentation and the examples that I can find, it seems that it would be

  fix to create a global table [outside any function] variable to load image names

  then use these images to a slide show. I want to do the dynamic application, modify the text file as a new series of images.

  The global variable passes zero [any value] after the load event listener. Why is this?

  Is not global and world alive for the duration of the SWF?

  PARAMS. TXT:

  monthNames = January, February, March, April, may, June, July, August, September, October, November, December of & dayNames = Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday

  CODE:

  var dNames:Array = new Array();
  var mNames:Array = new Array();
  var request: URLRequest = new URLRequest("images/params.txt");
  variable var: URLLoader = new URLLoader();
  variables.dataFormat = pouvez;
  variables.addEventListener (Event.COMPLETE, completeHandler);
  Try
  {
  variables. Load (request);
  }
  catch (error: error)
  {
  trace ("unable to load URL:" + error);
  }
  trace ("2 mNames 2:" + mNames [2]);
  trace ("2 dNames 3:" + dNames [3]);
  Stop();

  function completeHandler(event:Event):void
  {
  var loader: URLLoader = URLLoader (event.target);
  dNames = loader.data.dayNames.split(",");
  mNames = loader.data.monthNames.split (",");
  trace (Loader.Data.DayNames);
  trace ("1 mNames 2:" + mNames [2]);
  trace ("1 dNames 3:" + dNames [3]);
  }

  OUTPUT:

  2 mNames 2: undefined
  2 dNames 3: undefined
  Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday
  1 mNames 2: March
  1 dNames 3: Wednesday

  How to access these values after the loading of the external file, after charging?

  Thanks in advance.

  The statement you quoted all Adobe documentation is correct.

  If you want to load the data into the tables before anything else happens, then have everything that happens to run via the function completeHandler... when the data is loaded and processed in the tables.

  the command: loadFile() runs before the trace ("2:" + images [4]); command.  The loadFile function is processed and loading process BEGINS... but begins loading does not delay the main treatment to continue down the line - the loading itself becomes a secondary/background task.  The order was to run the function loadFile and the processing of this function has been completed.  If you don't believe, then add a trace...

  function loadFile (): void

  {

  vars.dataFormat = pouvez;

  vars.addEventListener (Event.COMPLETE, onComplete, false, 0, true);

  Vars.Load (new URLRequest("images/fnames.txt"));

  trace ("implementation");

  }

  If you add this trace, you will see the execution of function loadFile is completed and the following line in your code is then treatment... trace (2...)

  The addEventlistener method does not stop anything.  The addEventListener method code is assigned a monitor, not a traffic controller... it's say the monitor to indicate when the loading data are complete.  It does not do anything to stop the execution of the program.

  So if you want to wait until the data is loaded before anything else... it goes...

  function onComplete(evt:Event):void

  {

  var urlVars:URLVariables = evt.target.data;

  images = vars.data.images.split(",");

  tnails = vars.data.thumbnails.split(",");

  ................ HERE.................

  }

• global variable problem

  Hi all
  
  If I use this SELECTION 'C ' | myCodes. NEXTVAL INTO: ins2.code FROM DUAL; the trigger for insertion prior to the global variable does not work for this field: ins2.code...
  
  But if I use the validation key work but I want to use on insert before
  
  Here's my trigger validation key codes
  
  Start
  
  SELECT 'C ' | myCodes. NEXTVAL INTO: ins2.code FROM DUAL;
  If
  : ins2.name is not null
  then
  : global.name: =: ins2.name;
  : global.code: =: ins2.code;
  commit_form;
  end if;
  end;
  
  
  Please help me thanks in advance
  
  
  Sarah
  
  Published by: SarahSarahSarah on September 7, 2009 06:41

  Hi Sarah!

  The before insert trigger is triggered just at the moment where you call the commit_form build-in.
  So: ins2.code and: ins2.name are always set to null when you attempt to assign values to the globals.

  Place the code inside the direct trigger of prior insertion after the sequence - select.

  if
    :ins2.name is not null
  then
    :global.name := :ins2.name;
    :global.code := :ins2.code;
  end if;
  end;
  

  and the relaxation of the validation key:

  if
    :ins2.name is not null
  then
   commit_form;
  end if;
  end;
  

  or assign the values to the globals after the call to the commit_form build-in:

  if
    :ins2.name is not null
  then
    commit_form;
    :global.name := :ins2.name;
    :global.code := :ins2.code;
  end if;
  end;
  

  Concerning

  Published by: Magoo on 07.09.2009 13:47

• Using global variables in a device custom

  Hello world

  I have problems with the passing of data through my device customized using global variables. I want to allow a user to select a RIO device address when you set up the system definition file. This is recorded in a global variable using the hand Page VI. I would later use this RIO device address in RT driver to deploy a bitfile. I can hard-code, but it is much more convenient to use a global.

  When I try to store the address of the global variable, it updates the value temporarily (I confirmed that the structure of the event recognizes the change of value). When I click the node of the tree to define system linked to the Main Page VI and then click on it again, the hand Page VI runs again. I wrote the code to repopulate the address of device of RIO with the last value stored in the global variable, but it is empty. I've included the VI global variables in my build, so I can't imagine why it can reset this value.

  Any help would be appreciated!

  Thank you

  Mitch

  Have you tried to use the custom device properties to store this value instead of GVs?

  Configuration VI, you can set this property, and if I'm not mistaken, you can read these properties on the RT driver.

• DLL and global variables

  OK, here's a strange problem.  I am very new to create the dll, so I don't know that I have just an installation problem.

  But I'm trying to pass a global variable of a host program to its attached DLL.  I got this job when I was the CVI 2014. I recently upgraded to 2015 and then started getting "undefined symbols" errors.  With some struggle I managed to compile again, but broke the variable connection in the process.

  I have compiled my DLL in debug mode so that I walk in from the test project.  Right now, my global variable exists in the test project, as well as in the DLL.

  Can I export the variable and the use of DLLIMPORT/DLLEXPORT?  Confused and curiously not to find anyone quite like this on the forums.

  EDIT: this post stack overflow described pretty well from my experience.  I am linking statically.

  Well, what do you know?  I found my problem.  This draft article and example WERE vital to the solution.  This article called, "using the Export method qualifier"was also useful.  I'll cut to the Chase...

  If you use a qualifier of export on the definition and the import on the declaration, LabWindows/CVI identifier export symbol.

  This is the right key.

  So in my example, it should look like this:

  DLL fichier.c

  int DLLEXPORT varName = 0;

  Header.h DLL

  int DLLIMPORT varName;

  Project that uses DLL.c

  #include "header.h DLL.
  
  varName! = 1 ;  a method to change this variable for local use

  Pretty easy, huh?  But wow, it took some time to find.

• Addition of new global variables

  I change code that uses one or more global variables in a global folder of vi. I would like to add a few variables more and potentially change what exists and ask them to be in the same globals vi. I can easily add a variable of the same type by copying and pasting a variable of the same type on the Panel before the globals vi, but I can't add variables of different types.

  This post comes closest: http://forums.ni.com/t5/LabVIEW/how-to-associate-existing-global-variables/m-p/1079535/highlight/tru... but I did not understand this line:

  • Add FP (there may be several elements in a global variable VI)

  I read some of the warnings against the use of global variables as it can cause race conditions / lead to General illegibility. I'm curious what is recommended if global variables are used as the constants that are defined at the beginning of the program. In general, my LabVIEW code gets pretty unreadable if I have a lot of threads for all of these constants. Is there something better?

  Thank you!

  Kristen

  Hello kllurie,

  The scenario you mentioned (using globals to replace duplicate constants) is probably the best use cases for them - conditions of race etc. problems arise when they are used to the stream or in several scenarios of the writer.  Readability is perhaps a matter of concern, because it is not immediately clear what could be reading from or writing to a global when a thread would suffice.

  With regard to the modification of the globals vi, all you need to do is drop objects on the front of the range of controls (right click).

  Kind regards

• Dynamic read the global variable (cluster)

  Hello!

  I would like to lika to read each control (label and value) in my global variable that contains a cluster. The problem is that I am doing it on a cDAQ and insofar as I undestand and has seen property th node do not have good worl on a real-time target. The code that I've tested so far is as follows:

  

  It's the main/fornpanel on my cDAQ. The Subvi in the main code contains the following:

  

  The phenonomen I've seen against hepatitis a is that it works very well maybe the first and second time when I run cod drank for the third time that the labels are empty. I read something that the dose of propertynode does not correctly for real-time target, but it is a way to come to the same solution using only not not the propertynode or you could use the different propertynode?

  Best regards

  Anton

  I solved it by using a library (Cluster Toolkit of Autotestware) to the GE in variant tables and depending on the type, I converted the variant accordingly and saved.  I guess that CVT would be able to do, but since I already use the cluster and they are "already here" it was more convinient for me to use this solution.

• How to keep a relative path in a global variable

  Hello

  I use Teststand 2013 and 2013 of Labview

  Is it possible to set a relative path to a global variable in the Teststand? E.g. "... \vector1." HWS.

  Or should I use Labview functions to solve this problem?

  .

  Thank you

  The railways are much easier to handle in LabVIEW.  Thus, you can store the relative path as a string and then use LabVIEW to make the absolute path.

  I usually store a file into a global variable and then I can just concatinate the strings to build the absolute path.  For example:

  FileGlobals.Folder = "C:\\foo\\bar\\"
  
  Locals.Path = FileGlobals.Folder + "blah.txt".

• global variable functional to read and write data from and to the parallel loops

  Hello!

  Here is the following situation: I have 3 parallel while loops. I have the fire at the same time. The first loop reads the data from GPIB instruments. Second readers PID powered analog output card (software waveform static timed, cc. Update 3 seconds interval) with DAQmx features. The third argument stores the data in the case of certain conditions to the PDM file.

  I create a functional global variable (FGV) with write and read options containing the measured data (30 double CC in cluster). So when I get a new reading of the GPIB loop, I put the new values in the FGV.

  In parallel loops, I read the FGV when necessary. I know that, I just create a race condition, because when one of the loops reads or writes data in the FGV, no other loops can access, while they hold their race until the loop of winner completed his reading or writing on it.

  In my case, it is not a problem of losing data measured, and also a few short drapes in some loops are okey. (data measured, including the temperature values, used in the loop of PID and the loop to save file, the system also has constants for a significant period, is not a problem if the PID loop reads sometimes on values previous to the FGV in case if he won the race)

  What is a "barbarian way" to make such a code? (later, I want to give a good GUI to my code, so probably I would have to use some sort of event management,...)

  If you recommend something more elegant, please give me some links where I can learn more.

  I started to read and learn to try to expand my little knowledge in LabView, but to me, it seems I can find examples really pro and documents (http://expressionflow.com/2007/10/01/labview-queued-state-machine-architecture/ , http://forums.ni.com/t5/LabVIEW/Community-Nugget-2009-03-13-An-Event-based-messageing-framework/m-p/... ) and really simple, but not in the "middle range". This forum and other sources of NEITHER are really good, but I want to swim in a huge "info-ocean", without guidance...

  I'm after course 1 Core and Core 2, do you know that some free educational material that is based on these? (to say something 'intermediary'...)

  Thank you very much!

  I would use queues instead of a FGV in this particular case.

  A driving force that would provide a signal saying that the data is ready, you can change your FGV readme...  And maybe have an array of clusters to hold values more waiting to be read, etc...  Things get complicated...

  A queue however will do nicely.  You may have an understanding of producer/consumer.  You will need to do maybe not this 3rd loop.  If install you a state machine, which has (among other States): wait for the data (that is where the queue is read), writing to a file, disk PID.

  Your state of inactivity would be the "waiting for data".

  The PID is dependent on the data?  Otherwise it must operate its own, and Yes, you may have a loop for it.  Should run at a different rate from the loop reading data, you may have a different queue or other means for transmitting data to this loop.

  Another tip would be to define the State of PID as the default state and check for new data at regular intervals, thus reducing to 2 loops (producer / consumer).  The new data would be shared on the wires using a shift register.

  There are many tricks.  However, I would not recommend using a basic FGV as your solution.  An Action Engine, would be okay if it includes a mechanism to flag what data has been read (ie index, etc) or once the data has been read, it is deleted from the AE. 
  
  
  There are many ways to implement a solution, you just have to pick the right one that will avoid loosing data.
  

• Global variable control and simulation

  Hello!

  I have a probem with the export data of the Simulation loop in the graphic form.

  I have created a global variable, but in the façade is not updated or exported the data necessary, but in the file as a global variable do?

  I would like to gather (gathering) all the data after the simulation data file as Excel (trace the export data to Excel or save the spreadsheet file) as well as the image of terminal.

  Please find attached my files - someone has an idea or a solution?

  There must be some easy trick

  Thank you!

  Vasco

  (1) why are you doing this problem much more complex it must be using a global variable and another loop like that?

  (2) why you son of path of the VI in the picture? You try to crush the VI on disc with the image?

  (3) be careful not to ignore the output error.

  The code shown in the attached screenshot works very well. I'll take Bravo if it helped you.

  

• Functional Global Variable reference

  Hi all

  I want to update the value of the indicator element in primary VI, I don't want to use the global variable, due to the problem of race condition. So I create a functional global variable to control reference. It is reliable and can avoid the race condition critical?

  I have attached two Test VI.

  Thanks for your advice.

  Personally, I use user events to send data to the main VI and then he can update the indicator.  This generally works very well since most GUI screws using a Structure of the event anyway.